The use of interchangeable display sign systems is widespread in a variety of retailing industries, and is especially prevalent in restaurant and similar establishments where various items and their prices are subject to change on a relatively frequent basis. In many restaurants, a display sign system is often arranged adjacent a service counter where items are ordered, paid for, and delivered to the customer. Generally, these sign systems are backlighted with light sources mounted within the sign itself, while product and price information and similar indicia is provided as translucent characters and/or images on an otherwise opaque background. Light passes through the characters and illuminates the information in contrast to its opaque surroundings.
Examples of illuminated display signs are seen in U.S. Pat. No. 3,742,633 which issued to Bernhard Palm, and U.S. Pat. No. 3,458.945 which issued to L. N. Edwards. The Palm reference describes an illuminated display sign which includes individual characters which are placed between vertically spaced longitudinal rails. The rails are formed with a shallow channel and a deeper channel to enable insertion and removal of individual sign characters by sliding the same inwardly into the deeper channel until the character clears the upper portions of the lower rail, then pivoting the character inwardly toward the sign panel and sliding the lower end into the shallow groove. The insertion and removal of individual characters requires a rather intricate set of manipulations, requiring additional labor and time to achieve sign changes. Moreover, this arrangement requires the use of a biasing means to maintain adjacent characters in a tight relationship to prevent leakage of light between the individual characters, making insertion and removal of those characters more awkward and inconvenient.
The Edwards reference describes a display sign having a plurality of longitudinal protuberances designed to receive clips which support display indicia, as shown in the earlier Edwards U.S. Pat. No. 3,315,392. Such a mounting system for indicia is not contemplated for use in backlighted applications, however, as light leakage between adjacent indicia characters would be unacceptable. Furthermore, the use of the protuberance/clip support arrangement for the indicia characters is unduly complex, unwieldy and inefficient for display signs having a relatively large amount of information and indicia characters to be supported.
U.S. Pat. No. 4,367,604, which issued to Steven T. Porter, II, on Jan. 11, 1983, is directed to a backlighted menu board which has a plurality of vertically spaced ribs on the outer surface of its sign panel, and discusses the use of information strips which are insertable between the ribs. Porter further describes the provision of a plurality of picture display units which can be easily engaged with the flanges of two ribs of the sign, and which can be changed without dismantling a major portion of the sign. However, Porter requires that the lateral edges of its spaced ribs be substantially exposed to enable insertion or removal of its information strips therefrom. These exposed edges can allow undesirable leakage of light from the menu board.
Similar problems are encountered in sign systems as disclosed in U.S. Pat. No. 4,693,026, which issued to D. Callahan et al. on Sept. 15, 1987, and U.S. Pat. No. 4,765,080, which issued to W. Conti on Aug. 23, 1988. Both of these signs require insertion and/or removal of their letter panels from lateral side edges. Although the Callahan device includes a border member to minimize light leakage along its lateral edge, both of these changeable display devices require at least partial dismantling of the apparatus in order to change the information displayed thereon. As mentioned, because display signs of this type are often preferably mounted in close proximity to service counter areas critical to the operation of a restaurant or similar business, display signs requiring substantial labor and/or dismantling of the sign system are inefficient and obtrusive.
U.S. Pat. No. 4,682,430 which issued to Charles Ramsey on July 28, 1987, is an example of a removable price chip support arrangement designed to minimize light leakage. The price chip strip itself supports a plurality of individual price chips (i.e. 5) by providing a series of price chip receptor pockets fixedly attached adjacent one another. The strip is designed to be inserted between a pair of guide tracks mounted on the rear surface of a transparent frame panel which is provided on its front face with an opaque mask which defines elongated clear panels for display of the price chip indicia held within the price chip support strip. However, it is necessary to withdraw the price chip support strip from the support frame tracks to obtain access to the individual price chips held there within. Consequently, additional labor is required when changes are desirable, as the price chip support strip must be removed from the sign system. Moreover, because the support tracks are located on the rear face of the sign panel, access to the rear of the sign is required, further complicating sign change procedures, and often requiring the sign to be partially dismantled or opened.
Consequently, with sign systems heretofore available in the industry, it has been necessary to compromise the minimization of light leakage in an effort to provide access to the system for placing, removing, or otherwise changing information displayed thereon. Prior attempts to provide front access for changing the displayed information required complex structures and/or inconvenient manipulation of the indicia elements and other sign components, or compromised the light containment ability of the sign system, thereby diminishing the quality of the sign system and the efficiency of its use. Information changing procedures commonly interfered with business operations and added to the cost of operation through increased labor and capital outlays.